While this article is not a tabulation of current radar equipment and its specifications, some mention must be made of the variety of equipment that is available to the cruiser, particularly where antenna or scanner types are concerned. The scanner is the part that rotates, either in an exposed version or beneath a radome.
Cruising vessel radar scanners range in size from miniature, closed array dinner plate-sized models to four foot, open array semi-commercial units, and the difference in performance between these two radars is as dramatic as their appearance is disparate. In simplified terms, the smaller the antenna, the larger the horizontal beam width or HBW, and in this case larger is not better, because larger beam width equates to poorer target resolution (the HBW is the horizontal, fan-shaped pattern of signals that are transmitted from the antenna). For example, a radar whose antenna measures four feet across has an HBW of about 2°, while the dinner plate radar, one whose scanner unit measures twelve inches in diameter, offers an HBW of approximately 7.5°. This may seem inconsequential, it’s just a few degrees after all. Rest assured, however, if you are relying on your radar to separate closely spaced targets, such as the entrance to the aforementioned Newfoundland fjord, a breakwater or jetty, or two closely spaced vessels, then those few degrees will allow you to detect that opening or separation that much sooner and that much further away from the target. If, for instance, the opening represents 4° of arc at a given distance, then your twelve inch radar may not be able to detect it until you are close enough for it to represent more than 7.5 degrees of arc. Thus, if you seek the greatest resolution, then choose the largest scanner unit you can afford and reasonably install aboard your vessel.
Coupled with scanner size is range and power output. Larger scanners or invariably more powerful and have greater range. Remember, however, more often than not, you will use your radar on the one mile or less range. More often than not, it’s the targets that are close to you that you are concerned with. On occasion, you may use the maximum range to detect a distant landfall or large ship, but that’s the exception. More on range and scanner mounting options below.
Power output may also drive some, but not all, of your decision making process (most recreational vessel radars are offered in either 2 or 4 kW). More power may mean the ability to “see” better through rain and heavy fog and it affects the range factor as well. Additionally, higher power, 4kW radar typically has a lower threshold for return signal detection, in effect it “listens” better for a weaker return signal than its 2 kW brethren (4 kW radar antennas are larger and therefore more efficient at transmitting as well as receiving signals). In my opinion, however, you should choose your scanner type first, then let the range and power issue follow along. Remember, greater power output means greater power input and more amp hours consumed, an issue you’ll have to contend with particularly if you intend to use the radar often while under sail.